Technologies Under Development:

"Design and Development of Gas-Liquid Cylindrical Cyclone

Compact Separators for Three-Phase Flow"

Paper presented at:

1999 Oil and Gas Conference – Technology Options for Producers' Survival

June 28-30, 1999, Dallas, TX

Co-Sponsored by DOE and PTTC

by

Ram S. Mohan, Ph.D., Assistant Professor of Mechanical Engineering andOvadia Shoham, Ph.D., Professor of Petroleum Engineering

The University of Tulsa600 South College Avenue

Tulsa, Oklahoma 74104-3189Phone: (918) 631-2075

Email: Ram-Mohan@utulsa.edu

June 1999

2

Design and Development of Gas-Liquid Cylindrical Cyclone

Compact Separators for Three-Phase Flow

Ram S. Mohan, Ph.D. (Ram-Mohan@utulsa.edu, 918-631-2075)

Ovadia Shoham, Ph.D. (os@utulsa.edu, 918-631-3255)

Tulsa University Separation Technology Projects (TUSTP)

The University of Tulsa

600 South College Avenue

Tulsa, Oklahoma 74104-3189

BACKGROUND

Multiphase separation technology has advanced slowly and incrementally for several years.

A new look and infusion of novel ideas and concepts are now needed to develop breakthrough

technologies in this area for the 21st century. In the past, the petroleum industry has relied mainly

on the conventional vessel-type separator, which is bulky, heavy and expensive, to process

wellhead production of oil-water-gas flow. Economic and operational pressures continue to force

the petroleum industry to seek less expensive and more efficient separation alternatives in the

form of compact separators, such as the gas liquid cylindrical cyclone (GLCC©). The compact

dimensions, smaller footprint and lower weight of the GLCC has a potential for cost savings to

the industry, especially in offshore applications. Also, the GLCC reduces the inventory of

hydrocarbons significantly, which is critical for environmental and safety considerations.

A lack of understanding of the complex multiphase hydrodynamic flow behavior in the

GLCC inhibits complete confidence in its design and necessitates additional research and

development. Most of the studies on compact separators have been carried out for simple

gas/liquid flows, usually utilizing air and water. There has been considerable progress, recently,

in the research conducted in this area under the leadership of the Tulsa University Separation

Technology Projects (TUSTP), mainly for two-phase separation in the GLCC. The significance

of the research conducted by TUSTP has been highly appreciated by the industry, as shown by

their continuing support to the consortium. TUSTP research team provides expertise in several

essential areas, such as multiphase flow measurement and instrumentation, mathematical

modeling, fluid mechanics, computational fluid dynamics, process control and high pressure

field applications. Due to the much needed interdisciplinary nature of the research team, no

other industry/university research consortium exists in the area of compact multiphase separation

technology at the present time.

The objective of the proposed project is to expand the research activities of TUSTP to

multiphase oil/water/gas separation. This project will be executed in two phases. Phase I (1997

- 2000) will focus on the investigations of the complex multiphase hydrodynamic flow behavior

in a three-phase GLCC. The activities of this phase will include the development of a

mechanistic model, a computational fluid dynamics (CFD) simulator, and detailed

experimentation on the three-phase GLCC. The experimental and CFD simulation results will be

suitably integrated with the mechanistic model. In Phase II (2000 - 2002), the developed GLCC

separator will be tested under high pressure and real crudes conditions. This is crucial for

validating the GLCC design for field application and facilitating easy and rapid technology

deployment. Design criteria for industrial applications will be developed based on these results

3

and will be incorporated into the mechanistic model by TUSTP. These essential ingredients will

ensure the development of the state-of-the-art technology in compact separation technology for

the 21st century.

INTRODUCTION

For many years, the Petroleum Industry has relied mainly on the conventional vessel-type

separators. They are bulky, heavy and expensive in capital, installation and operation. Due to

economic and operational pressures, the petroleum industry has recently shown interest in the

development of innovative alternatives to the conventional separators. One such alternative is

the Gas-liquid Cylindrical Cyclone (GLCC). Unlike the conventional vessel type separators, the

GLCC is simple, compact, low weight, low-cost, requires little maintenance, and is easy to

install and operate. It is therefore gaining popularity as an easy-to-operate economically

attractive, alternative to the conventional separator. The development ranking of the various

separation technology alternatives are shown schematically in Fig. 1. As shown in this figure,

conventional vessel-type separators have reached their maturity, except for some minor

improvements that are being incorporated, such as new developments of internal devices and

control systems. Large diameter vertical cyclones and hydro-cyclones have also been used by

the industry for some time. However, recent trends in development are focused towards new

type of compact separators such as the GLCC.

Dev

elop

men

t

GLCC’s

FWKO

Cyclones

Emerging

Gas Cyclones

Conventional

Horizontal and Vertical

Separators

Growth

Finger Storage

Slug Catcher

Vessel Type

Slug Catcher

Maturity

Time

Hydrocyclones

Fig. 1 - ‘S’ Curve for Developmental Ranking of Separation Technology

A schematic of the GLCC separator is shown in Fig. 2. It is a vertically installed pipe

mounted with a downward inclined tangential inlet, with outlets provided at the top and bottom

of the pipe. It has neither moving parts nor internal devices. Due to the tangential inlet, the flow

forms a swirling motion producing centrifugal forces. The two phases of the incoming mixture

are separated due to centrifugal and gravity forces. The liquid is forced radially towards the

walls of the cylinder and is collected from the bottom, while the gas moves to the center of the

cyclone and is taken out from the top. Currently, the GLCC finds its potential applications as a

gas knockout system upstream of production equipment. Through the control of Gas Liquid

Ratio (GLR), it enhances the performance of multiphase meters, multiphase flow pumps, and

de-sanders. Other applications are portable well testing equipment, flare gas scrubbers, and slug

4

catchers. The GLCC is also being considered for down hole separation, primary surface

separation (onshore and offshore) and sub sea separation.

Fig. 2 - Gas-Liquid Cylindrical Cyclone Configuration

GLCC’s that have already been installed and put to use in the field have successfully

demonstrated their applicability as two-phase separators. The concept is bound to have a

pronounced impact on the petroleum industry. However, a lack of understanding of the

complex, multiphase, hydrodynamic flow behavior inside the GLCC inhibits complete

confidence in the GLCC design and necessitates additional research and development.

Knowledge of the hydrodynamic behavior would enable GLCC users to correctly predict the

performance of the GLCC and to carry out appropriate design for all configurations and

applications.

Most of the studies on compact separators have been carried out for simple gas/liquid flows,

usually utilizing air and water. The fluid system existing in the industry is much more

complicated with oil/water/gas three-phase flow. In this project, we propose to develop compact

separators for oil/water/gas flow and conduct detailed investigations of the three-phase flow

behavior. Initially, oil/water two-phase flow will be studied, utilizing a non emulsifying oil to

avoid emulsions and dispersions. By all means, this will not be a trivial extension of gas/liquid

flow due to the close densities of the two liquids, water and oil. Later, the gas phase will be

added to investigate whether compact separators will be effective as a water knockout device to

remove the majority of the free water from multiphase mixtures.

OBJECTIVES

The overall objective of this five-year project (October, 1997 – September, 2002) is to expand

the state-of-the art of compact separation technology research from two-phase (gas-liquid) flow

separation to multiphase oil/water/gas flow production systems. The research aims at making

compact separators predictable, reliable and a viable economical alternative to conventional vessel

type separators. Long-term cooperation with petroleum industry is envisaged in conducting this

project to better understand, analyze and design compact separators for field application, and

facilitate easy and rapid technology deployment.

5

PROJECT DESCRIPTION

This project will be executed in two phases. Phase I (1997 - 2000) will focus on the

investigations of the complex multiphase hydrodynamic flow behavior in a three-phase GLCC©

separator. The activities of this phase will include the development of a mechanistic model, a

computational fluid dynamics (CFD) simulator, and detailed experimentation on the three-phase

GLCC©. The experimental and CFD simulation results will be suitably integrated with the

mechanistic model. In Phase II (2000 - 2002), the developed GLCC© separator will be tested under

high pressure and real crudes conditions. Design criteria for industrial applications will be

developed based on these results and will be incorporated into the mechanistic model.

Major Project Milestones:• Initial modeling, design, fabrication and preliminary data acquisition (Year 1)

• Gas carry-under measurements, model refinement and design improvement (Year 2)

• Liquid carry-over measurements, model refinement and design improvement (Year 3)

• High-pressure field pilot plant GLCC© design (Year 4)

• High-pressure data acquisition and field design guidelines (Year 5)

• Interim and final reports preparation (ongoing).

PROJECT STATUS

This report presents a brief overview of the activities and tasks accomplished during Year 1

of the project (budget period, October 1, 1997 – September 30, 1998). The total tasks of the

budget period are given initially, followed by the technical and scientific results achieved till

date. The report concludes with a detailed description of the plans for the conduct of the project

for the upcoming budget period (October 1, 1998 – September 30, 1999).

Tasks of the Current Budget Period (Oct. 1, 1997 – Sept. 31, 1998)

Objective - Initial Modeling and Data Acquisition:

a. Initial development of the mechanistic model for three-phase separation.

b. Design and expansion of two-phase test facility for three-phase loop.

c. Preliminary experimental data acquisition of global separation efficiency.

d. Preliminary simulation of three-phase flow using CFX code.

e. Interim reports preparation.

As a part of the tasks identified for the current budget period, the following specific activities

have been completed:

1. Plans for detailed experimental investigations for GLCC© control are in progress.

Preliminary data acquisition is in progress for control strategy formulation. The

experimental investigations are being conducted in the out-door experimental facility using a

dedicated GLCC© capable of withstanding higher pressures. The newly fabricated GLCC

©

with state-of-the-art control valves and new data acquisition system have already been

installed. This GLCC© has a new aluminum inlet, designed for high-pressure (200-psi)

conditions, with sector/slot plate configuration.

2. Identified a new indoor project location for the experimental facility for three-phase flow in

the North Campus of The University of Tulsa and allocated the area. Updated the

6

preliminary floor layout drawing to scale of the three-phase flow loop consisting of the three-

phase separator, oil and water tanks, metering section, test section and, related valves and

fittings. Construction of the three-phase flow loop is in progress and expected to be

completed by November-December, 1998.

3. Started development activities to identify strategies for mechanistic modeling for multiphase

flow behavior in GLCC©. Literature review in progress to identify the issues related to

behavior of oil-in-water and water-in-oil dispersions. Several oil/water-mixing strategies

formulated based on Computational Fluid Dynamics (CFD) simulation studies. Investigation

in progress to identify techniques for integration of GLCC©s with hydrocyclones for building

three-phase compact separation systems. This is very critical for elevating the compact

separation technology from bulk separation to fine separation of three-phase flow.

4. Several items for the flow loop partially received. Procurement of components needed for

the flow loop such as pipes and fittings, gate valves, pumps, and control valves is completed.

Three-phase separator, oil and water tanks, two sets of centrifugal pumps for oil and water,

flexible piping and the upstream metering section have been installed. Fabrication of the

flow loop, support structure for the experimental facility, test GLCCs and downstream

metering section are underway.

5. Designated four graduate students to perform the research and experiments. One more

student is expected to join in Spring '99.

It is essential to develop an appropriate control strategy for proper operation of a three-

phase GLCC. Hence initial experimental investigations are planned for evaluating the GLCC

control system performance for different possible control strategies. The layout of the

experimental facility for conducting the controls experiments is given in Fig. 3. Construction of

the dedicated GLCC for controls investigation is completed in the existing outdoor GLCC flow

loop and the experiments are in progress.

A schematic of the floor layout of the three-phase flow loop consisting of the metering

and test section are shown in Figs. 4 and 5. Air is supplied from a compressor and is stored in a

high-pressure gas tank. The air flows through a metering section consisting of micro-motion

mass flow meter and control valves. The liquid phases (water and oil) are pumped from the

respective storage tanks and are metered with two sets of micro-motion mass flow meters and

control valves, before being mixed. Several mixing sections have been designed to evaluate and

control the oil-water mixing characteristics at the inlet. The liquid and gas phases are then mixed

at a tee junction and sent to the test section. State-of-the-art micromotion net oil computers

(NOC) will be used to quantify the watercut, GOR, and mixture density. The test section

consists of 2 dual stage GLCCs. Initially the test section will be equipped with one dual stage

GLCC and later it will be upgraded to 2 dual stage GLCCs. The three-phases from the GLCC

outlets will also metered using micro-motion mass flow meters. The test section construction

will be modular so that in place of GLCC any other separators such as hydro-cyclones could be

used in series to form compact separation systems.

Investigations have been initiated in collaboration with the TUSTP member companies

and other universities such as Michigan State University to formulate mechanistic models for

integrated compact separation systems. Control valves placed along the flow loop control the

flow into and out of the test sections. The flow loop is also equipped with several temperature

7

sensors and pressure transducers for measurement of the in-situ pressure and temperature

conditions. Installation of the data acquisition system will follow as soon as the construction of

the flow loop is completed. A schematic of the typical data acquisition system for the flow loop

is shown in Fig. 6.

Three types of GLCC configurations will be considered for single stage GLCC and dual

stage GLCC as shown in Fig. 7. The above flow loop can be used for both configurations. These

two types of configurations will aid in investigating the function of GLCC as a bulk separator

and a full separator. Non-emulsifying oil will be used as the experimental fluid. Flow runs will

be conducted initially by using oil-water two-phase and gas will be added as the third phase later.

Two types of oil-water interface are possible as shown in Fig. 8. Initial investigation will focus

on identifying the nature of oil-water interface and formulation of appropriate separation

strategies for the GLCC. Several literature have been identified to provide more information into

the nature of the oil-water interface for cyclonic separators of low G-forces such as the GLCCs.

As an essential component of the mechanistic model development for three-phase flow,

preliminary Computational Fluid Dynamic simulations have been conducted to investigate the

oil-water separation in a two-phase liquid-liquid mixture with water (denser liquid) as the

medium. The results of CFD flow-simulation studies using the computer code CFX 4.1 are

shown in Fig. 9 for three different oil droplet sizes. The simulation time was 20 seconds, the oil

specific gravity was 0.885, and the GLCC lower part length and diameter were 4-ft and 3-inches

respectively. The magnitudes of radial, axial and tangential velocity components are also given

in Fig. 9, which is typical of normal GLCC operating conditions. The simulation results of the

droplet trajectory indicate that, it is much easier to separate oil droplets of diameters 1000 micron

(1mm) and above from the denser water medium. It is also observed that at diameters of 100

microns and below there is a much higher probability of oil particle carry-under into the water

stream. This is a very significant initial result as it gives a basis for oil droplet monitoring,

predicting the oil carry-under and developing strategies for ensuring separation efficiency of

three-phase separators. Detailed investigations are planned in the second project year (October,

1998 – September, 1999) to conduct simulation studies for other operating conditions, namely

different flow velocities, different fluid densities, and also verification with experimental results.

Tasks of the Second Project Year Activities (Oct. 1, 1998 - Sep. 31, 1999)

Objective - Gas Carry-under and Model Refinement:

a. Measurement of the operational envelope of the GLCC for gas carry-under.

b. Detailed measurement of gas carry-under beyond the operational envelope.

c. Development of constitutive models for CFD code for simulation of gas carry-under.

d. Refinement of mechanistic model for gas carry-under.

e. Investigation of three-phase separator configurations and verification with experimental

results.

f. Interim reports preparation.

Contract Information: Grant No.: DE-FG26-97BC15024, Project Period: 10/1/97 to 09/30/02,

Recipient Project Director: Dr. Ram S. Mohan, The University of Tulsa, Ph: 918-631-2075, Fax:

918-631-2397, Email: Ram-Mohan@utulsa.edu.

8

Acknowledgement: The authors wish to acknowledge the Federal Energy Technology Center

(FETC), U.S. Department of Energy for the above grant and specifically the DOE Project

Officers, Ms. Rhonda P. Lindsey and Mr. James L. Barnes at the National Petroleum Technology

Office (NPTO), Tulsa. This report is prepared for the project period 10/1/97 to 09/30/98.

Note: GLCC© - Gas-Liquid Cylindrical Cyclone - copyright, The University of Tulsa, 1994.

LCV

GCV

Multiphase Flow Inlet Liquid Outlet

Gas Outlet

DP

AP

Fig. 3. GLCC Experimental Facility for Controls Experiment

9

3-PHASE

GRAVITY

SEPARATOR

WATER

TANK

PUMP

COMPRESSOR

HIGH PRESSURE

GAS TANK

Fig.4. Three-Phase Experimental Flow Loop

PUMP

TE

ST

SE

CT

ION

OIL TANK

INDOOR PROJECT AREA

AIR

PRESSUREREGULATOR TEMPERATURE

TRANSDUCER

MIXING UNIT

WATER LINE

OIL LINE

AIR

V1 MV1

GAS METERING SECTION

MM

GAS CONTROL

V2 V3

V4

CV1

DV1

TT1

TT2

OIL METERING SECTION

MM

OIL CONTROL

V5 V6

V7

CV2MV2

WATER METERING SECTION

MM

WATER CONTROL

V8 V9

V10

CV3MV3

PG1

PG2

PG4PG3

PG5 PG6

TT3

DV2

DV3

PG7

BY

PA

SS

LIN

E

V11

V12

V13

V14

V15

V16 V17

V18 V19

DV4

V20

V21

V22

V24

V26

V25

OIL SKIMMER

V23

OilMixture

GLCC

GLCC

GLCC

GLCC

Water

M

M

M

Air

Fig. 5. GLCC Test Section

10

Fig.6 Instrumentation and Data Acquisition Flow Chart (3-PHASE)

Gas Metering

Test Section

Output Board

Multiplexer (AMUX-64) Input

Computer

Monitor

Printer

Key Board

4 - 20 to0 - 10

Gas, Oil and Water Flow Rate Control

3 CVs3 TMs 3 CVs

2 MMs

3 ATs

6 APs

1 DP

ValidyneDemodulator Case

1 AT

Oil Metering

1 AT

1 MM

1 MM

On / Off Switch

Actuator Ball Valves

ManualControl

Water Metering

1 AT

1 MM

1VS

11

Fig. 7 Test section configurations (separated outlets)

Case 1:

Single Stage

Case 2:

Two StageFrom TheLiquidOutlet

Water

Oil+Water

Oil

Water

Oil+Water

Three-phase Flow

Gas

Gas

Three-phase Flow

Gas

Three-phase Flow

Water

Water

Oil

Case 3:

Two Stage From

The Oil Outlet

Oil+Water

Case 1Case 1

GASGAS

LIQUIDLIQUID

Oil / Water Interface??

GASGAS

LIQUIDLIQUID

Case 2Case 2

Fig. 8 Oil/Water Interface

12

1000 Microns 300 Microns 100 Microns

Inlet

Outlet

GLCC

Axis

Simulation Time : 20 seconds, GLCC diameter: 3 inches,

GLCC Lower length: 4 Ft, Radial Velocity: 0.18 m/s,

Axial Velocity: 0.75 m/s, Tangential Velocity: 1.66 m/s,

Oil Density: 885 Kg/m3,

Fig. 9 Preliminary Droplet Trajectory Analysis

Design and Development of Gas-LiquidCylindrical Cyclone Compact

Separators for Three-Phase Flow

Design and Development of Gas-LiquidDesign and Development of Gas-LiquidCylindrical Cyclone CompactCylindrical Cyclone Compact

Separators for Three-Phase FlowSeparators for Three-Phase Flow

1999 Oil & Gas Conference1999 Oil & Gas Conference1999 Oil & Gas Conference

byRam S. Mohan and Ovadia Shoham

The University of TulsaJune 28-30, 1999

byRam S. Mohan and Ram S. Mohan and Ovadia ShohamOvadia Shoham

The University of TulsaJune 28-30, 1999June 28-30, 1999

IntroductionIntroductionIntroduction

❖ Past Studies on Compact GLCCPast Studies on Compact GLCC©© Separators Have Separators Have Been Carried Out for Two-Phase Gas/Liquid flowBeen Carried Out for Two-Phase Gas/Liquid flow

❖❖ Partial or Full Separation of Gas and Liquid Partial or Full Separation of Gas and Liquid Successfully Demonstrated by the GLCCSuccessfully Demonstrated by the GLCC©©

❖❖ Extension of GLCC Extension of GLCC©© Capabilities for Oil/Water/Gas Capabilities for Oil/Water/Gas Three-Phase Separation.Three-Phase Separation.

❖❖ Feasibility for Bulk Separation of Water and Oil Feasibility for Bulk Separation of Water and Oil Phases.Phases.

ObjectiveObjective

❖❖Study Oil/Water/Gas Three-Phase GLCCStudy Oil/Water/Gas Three-Phase GLCCCompact Separators:Compact Separators:

"" Design and Construct Three-Phase FlowDesign and Construct Three-Phase FlowLoopLoop

"" Acquire Experimental DataAcquire Experimental Data

"" Develop a Mechanistic ModelDevelop a Mechanistic Model

"" Test at High Pressure and Real Crude FieldTest at High Pressure and Real Crude FieldConditionsConditions

❖❖GLCC as Bulk SeparatorGLCC as Bulk Separator?

Project Scope and Schedule- Phase IProject Scope and Schedule- Phase I

"October 1997 - September 2000 at TheUniversity of Tulsa (TU)

"Design and Construct Three-Phase GLCCLoop

"Acquire Experimental Data on Oil-WaterSeparation Efficiency

"Conduct CFD Simulation and DevelopMechanistic Model

"Develop User Friendly Computer Code forDesign

❖ October 2000 - September 2002 at TU and Texas A&M

" Test New GLCC Under High Pressure, andReal Crudes - Texas A&M

" Modify Mechanistic Model, Design Criteriaand Computer Code - TU

Project Scope and Schedule- Phase IIProject Scope and Schedule- Phase II

Experimental ProgramExperimental Program

❖ Experimental Facility

"Metering and Mixing Section

"Test Section

❖ Three-Phase GLCC Design

Metering and Mixing SectionMetering andand Mixing Section

Air

Pum

p MM

Oil

tank

Pum

p MM

Water

tank

MM

Water

Mixture

Oil

Air

GLCC Test SectionGLCC Test SectionSectionMixture

GLCC

GLCC

GLCC

GLCC

MM

MM

MM

To

separator

OilAir Water

Data Acquisition SystemData Acquisition System

Test Section

Output Board

Multiplexer (AMUX-48) Input

Computer

Monitor

Printer

Key Board

4 - 20 mA

4 CVs

2 ATs

6 APs

2 DP Inlet Metering

4 MM

3 CV

OutletMetering

3 MM

Data Acquisition SystemData Acquisition System

GLCC ConfigurationsGLCC Configurations

❖ Two types of configuration will beconsidered

" Single-Stage GLCC

" Two-Stage GLCC

Case 1:

Water Rich

Oil Rich

Gas

Three-phase Flow

Single-Stage GLCC Single-Stage GLCC

Case 2: Oil

Water

Oil+Water

Three-phase Flow

Gas

Two-Stage GLCC© / LLCC© Two-Stage GLCC© / LLCC©

Three-Phase GLCC Design Three-Phase GLCC Design

Project StatusProject Status

❖❖ Design and Construction of New Three-PhaseDesign and Construction of New Three-PhaseFlow Loop - CompletedFlow Loop - Completed

❖❖ Instrumentation and Data Acquisition System -Instrumentation and Data Acquisition System -CompletedCompleted

❖❖ Oil-Water Runs - In ProgressOil-Water Runs - In Progress

❖❖ Three-Phase GLCC Design - In ProgressThree-Phase GLCC Design - In Progress

Overview of Three-PhaseFlow LoopOverview of Three-PhaseFlow Loop

Oil, Water and Gas LinesOil, Water and Gas Lines

Oil-Water MixingOil-Water Mixing

Downstream MeteringDownstream Metering

LLCC© in PlaceLLCC© in Place

Oil/Water Separationin LLCC©Oil/Water Separationin LLCC©

Conclusions & NearFuture WorkConclusions & NearFuture Work

❖ Oil/Water Mixtures Can be Separated in theLLCC© with Efficiencies Greater than 80%.

❖❖ Summer 1999Summer 1999"" Construction and Installation of Three-Construction and Installation of Three-

Phase GLCCPhase GLCC"" Preliminary Data AcquisitionPreliminary Data Acquisition

❖❖ Fall 1999Fall 1999"" Completion of Data AcquisitionCompletion of Data Acquisition"" Initial Mechanistic ModelInitial Mechanistic Model